On paper, southern Israel has never been safer. On Sunday, for the first time, the Israel Defence Forces deployed its cutting edge missile defence system which is meant to be able to block rockets fired by militants in Gaza.

Israel started developing the system in 2007 and, from the beginning, expectations were enormous. Developers set the bar high with its name: Iron "kippah", conjuring up the image of a huge impenetrable skullcap that would allow the Gaza envelope communities to carry on life as normal even as rockets rained down.

But on Sunday, military and political leaders were at pains to lower expectations of the Iron Dome, as it is known outside Israel, which is now in place just outside Beersheba.

Doron Gavish, commander of the Israel Air Force Air Defence Division, said that it provides "good but not hermetic" protection. Prime Minister Binyamin Netanyahu told the cabinet that while the Iron Dome will help Israel to deal with the problem of rocket fire, he did not want to create the "illusion" that it will provide a "full or comprehensive answer".

The big question bothering analysts - and, of course, the answer is highly classified - is how many rockets per minute the system can handle. If it can handle, for example, 50 a minute, it would seem that militants could simply fire 51. In short, the Iron Dome will not provide protection at all - it will just make militants work harder to generate the same fear and damage on the Israeli side.

Then there is the issue of cost. The interceptors that the Iron Dome fires are notoriously expensive, while the rockets are notoriously cheap. Though the figures are not clear, it is quite possible a rocket from Gaza costs under £100, while intercepting it costs many times more.

Putting these two issues together, the Iron Dome could actually be good for militants. They may lose little of their ability to affect life on the Israeli side, while getting the bonus of a new way to bleed Israel's economic resources.

Over recent months, it has seemed possible that Israel would not deploy the system to protect civilians at all, and instead reserve it for military targets. Mayors in southern Israel were outraged, and threatened legal action against the government. On Sunday they got their wish, but it seems that their victory may be a hollow one.

It is possible that the deployment of the Iron Dome may actually increase rocket fire for a while, because just like Israeli analysts - and civilians for that matter - Gaza militants are desperate to know what kind of rocket traffic the system can handle. And they know there is only one way to find out.